Control method of movable body, exposure method, device manufacturing method, movable body apparatus, and exposure apparatus

ABSTRACT

In a beam irradiation apparatus in which a movable body holds an object, a mark detection system detects a first mark on the movable body while moving the movable body in a first direction and changing an irradiation position of a measurement beam in the first direction, the mark detection system detects a second mark while moving the movable body in the first direction and changing the irradiation position of the measurement beam in the first direction, a controller controls a position of the movable body in a second direction intersecting the first direction during a time period between the detection of the first mark and the detection of the second mark, and the controller controls the movement of the movable body to adjust a positional relation between the object on the movable body and a processing beam, based on results of the detection of the first and second marks.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 16/019, 662filed Jun. 27, 2018, which is a divisional of U.S. patent applicationSer. No. 15/627, 966 filed Jun. 20, 2017 (now U.S. Pat. No. 10,036,968), which in turn is a continuation of International Application No.PCT/JP2015/085050, with an international filing date of Dec. 22, 2015.The disclosure of each of the above-identified prior applications ishereby incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to control methods of movable bodies,exposure methods, device manufacturing methods, movable bodyapparatuses, and exposure apparatuses, and more particularly to acontrol method of a movable body on which an object provided withplurality of marks is placed, an exposure method including the controlmethod of the movable body, a device manufacturing method using theexposure method, a movable body apparatus including a movable body onwhich an object provided with a plurality of marks is placed, and anexposure apparatus equipped width the movable body apparatus.

Description of the Background Art

Conventionally, in a lithography process for manufacturing electronicdevices (micro devices) such as semiconductor devices (integratedcircuits and the like), and liquid crystal display devices, a projectionexposure apparatus of a step-and-scan method (a so-called scanningstepper (which is also called a scanner)) and the like are used.

In this type of exposure apparatuses, for example, since plural layersof patterns are formed and overlaid on a wafer or a glass plate(hereinafter, generically referred to as a “wafer”), an operation (aso-called alignment) for optimizing a relative positional relationshipbetween a pattern already formed on the wafer and a pattern that a maskor a reticle (hereinafter, generically referred to as a “reticle”) hasis performed. Further, as an alignment sensor used in this type ofalignment, the one that is capable of promptly performing detection of agrating mark provided on the wafer by scanning a measurement beam withrespect to the grating mark (causing the measurement beam to follow themovement of wafer W) is known (e.g., refer to U.S. Pat. No. 8,593,646).

Here, also in order to improve the overlay accuracy, it is desirable toperform position measurement of the grating mark a plurality of times,and specifically, it is desirable to accurately and speedily perform theposition measurement of grating marks in all of shot areas set on thewafer.

SUMMARY OF THE INVENTION

According to a first aspect, there is provided a control method of amovable body, comprising: detecting a first mark of a plurality of marksprovided at an object placed on a movable body while scanning ameasurement beam in a direction of a first axis with respect to thefirst mark, as moving the movable body in the direction of the firstaxis, the measurement beam being irradiated from a mark detectionsystem; measuring a positional relationship between the first mark andthe measurement beam; and adjusting a relative position between themeasurement beam and the movable body in a direction of a second axis,on the basis or the positional relationship that has been measured, thesecond axis intersecting the first axis.

According to a second aspect, there is provided an exposure method,comprising: controlling the movable body on which an object providedwith a plurality of marks is placed, with the control method of themovable body related to the first aspect; and forming a predeterminedpattern on the object by irradiating the object with an energy beam, ascontrolling a position of the movable body within a two-dimensionalplane that includes the first axis and the second axis on the basis of adetection result of the plurality of marks.

According to a third aspect, there is provided a device manufacturingmethod, comprising: exposing a substrate using the exposure methodrelated to the second aspect; and developing the substrate that has beenexposed.

According to a fourth aspect, there is provided a movable bodyapparatus, comprising: a movable body that is movable within atwo-dimensional plane including a first axis and a second axisintersecting the first axis; a mark detection system that scans ameasurement beam in a direction of the first axis, with respect to aplurality of marks provided at an object placed on the movable body; anda control system that performs detection of the marks using the markdetection system, as moving the movable body in the direction of thefirst axis, wherein the control system detects a first mark of theplurality of marks, and also measures a positional relationship betweenthe first mark and the measurement beam and adjusts a relative positionbetween the measurement beam and the movable body in a direction of thesecond axis, on the basis of the positional relationship that has beenmeasured.

According to a fifth aspect, there is provided an exposure apparatus,comprising: the movable body apparatus related to the fourth aspect, inwhich an object provided with a plurality of marks is placed on themovable body; and a pattern forming apparatus that forms a predeterminedpattern on the object by irradiating the object placed on the movablebody with an energy beam, a position of the movable body within thetwo-dimensional plane being controlled on the basis of a detectionresult of the plurality of marks.

BRIEF DESCRIPTION OF DRAWINGS

In the accompanying drawings;

FIG. 1 is a view schematically showing a configuration of an exposureapparatus related a first embodiment;

FIG. 2a to FIG. 2c are views showing examples (No. 1 to No. 3) ofgrating marks formed on a wafer;

FIG. 3 is a view showing a configuration of an alignment system equippedin the exposure apparatus in FIG. 1;

FIG. 4 is a plan view of readout diffraction gratings equipped in thealignment system in FIG. 3;

FIG. 5a is a view showing an example of a waveform generated on thebasis of the output of a detection system equipped in the alignmentsystem in FIG. 3, FIG. 5b is a view showing a waveform obtained byadjusting a lateral axis of the waveform in FIG. 5a , and FIG. 5c is aconcept view of the way of obtaining the position of a grating mark onthe wafer;

FIG. 6 is a block diagram showing a control system of the exposureapparatus;

FIG. 7 is a flowchart used to explain an exposure operation using theexposure apparatus in FIG. 1;

FIGS. 8a to 8c are views (No. 1 to No. 3) used to explain an alignmentmeasurement operation and a focus mapping operation;

FIG. 9 is a flowchart used to explain an alignment measurementoperation;

FIG. 10 is a view used to explain a relative relationship between awafer stage and a measurement beam of the alignment system during thealignment measurement operation;

FIG. 11 is a view showing an example of a drive signal of a movablemirror equipped in the alignment system in FIG. 3;

FIGS. 12a to 12d are views (No. 1 to No. 4) used to explain an alignmentmeasurement operation in an exposure apparatus related to a secondembodiment;

FIG. 13 is a flowchart used to explain an exposure operation in thesecond embodiment;

FIG. 14 is a flowchart used to explain an alignment measurementoperation in the second embodiment;

FIG. 15a is a view showing a measurement beam from an alignment systemthat is incident on a grating mark and a diffraction beam related to amodified example, and FIG. 15b and FIG. 15c are views (No. 1 and No. 2)showing the positions of the measurement beams and the diffraction beamson a pupil plane of an objective lens; and

FIG. 16 is a view showing a modified example of detection system of analignment system.

DESCRIPTION OF EMBODIMENTS First Embodiment

A first embodiment will be discussed below, on the basis of FIGS. 1 to11.

FIG. 1 schematically shows a configuration of an exposure apparatus 10related to the first embodiment. Exposure apparatus 10 is a projectionexposure apparatus of a step-and-scan method, which is a so-calledscanner. As will be described later, in the present embodiment, aprojection optical system 16 b is provided, and in the descriptionbelow, the explanation is given assuming that a direction parallel to anoptical axis AX of projection optical system 16 b is a Z-axis direction,a direction in which a reticle R and a wafer W are relatively scannedwithin a plane orthogonal to the Z-axis direction is a Y-axis direction,a direction orthogonal to the Z-axis and the Y-axis is an X-axisdirection, and rotation (tilt) directions around the X-axis, the Y-axisand the Z-axis are θx, θy and θz directions, respectively.

Exposure apparatus 10 is equipped with an illumination system 12; areticle stage 14; a projection unit 16; a wafer stage device 20including a wafer stage 22; a multipoint focal position measurementsystem 40; an alignment system 50; control system thereof; and the like.In FIG. 1, wafer W is placed on wafer stage 22.

As is disclosed in, for example, U.S. Patent Application Publication No.2003/0025890 and the like, illumination system 12 includes: a lightsource; and an illumination optical system that has an illuminanceuniformizing optical system having an optical integrator, and a reticleblind (none of which is illustrated). Illumination system 12 illuminatesan illumination area IAR having a slit-like shape elongated in theX-axis direction on reticle R set (restricted) by the reticle blind (amasking system) with illumination light (exposure light) IL with almostuniform illuminance. As illumination light IL, for example, an ArFexcimer laser beam (with a wavelength of 193 nm) is used.

On reticle stage 14, reticle R having a pattern surface (a lower surfacein FIG. 1) on which a circuit pattern and the like are formed is fixedby, for example, vacuum adsorption. Reticle stage 14 is finely, drivablewithin an XY plane and also drivable at a predetermined scanningvelocity in scanning direction (the Y-axis direction that is a lateraldirection on the pare surface of FIG. 1), with a reticle stage drivesystem 32 (not illustrated in FIG. 1, see FIG. 6) including, forexample, a linear motor and the like. Positional information within theXY plane (including rotation amount information in the θz direction) ofreticle stage 14 is constantly measured at a resolution of, for example,around 0.5 to 1 nm with a reticle stage position measurement system 34including, for example, an interferometer system (or an encoder system).The measurement values of reticle stage position measurement system 34are sent to a main controller 30 (not illustrated in FIG. 1, see FIG.6). Main controller 30 controls the position (and the velocity) ofreticle stage 14 by calculating the position of reticle stage 14 in theX-axis direction, the Y-axis direction and the Oz direction on the basisof the measurement values of reticle stage position measurement system34 and controlling reticle stage drive system 32 on the basis of thiscalculation result. Further, exposure apparatus 10 is equipped with areticle alignment system 18 (see FIG. 6) for performing detection ofreticle alignment marks formed on reticle R, though the reticlealignment system is not illustrated in FIG. 1. As reticle alignmentsystem 18, an alignment system having a configuration as disclosed in,for example, U.S. Pat. No. 5,646,413, U.S. Patent ApplicationPublication No. 2002/0041377 and the like can be used.

Projection unit 26 is disposed below reticle stage 14 in FIG. 1.Projection unit 16 includes a lens barrel 16 a and projection opticalsystem 16 b stored within lens barrel 16 a. As projection optical system16 b, for example, a dioptric system composed of a plurality of opticalelements (lens elements) arrayed along optical axis AX parallel to theZ-axis direction is used. Projection optical system 6 b is, for example,both-side telocentric, and has a predetermined projection magnification(such as ¼ times, ⅕ times or ⅛ times). Therefore, when illumination areaIAR on reticle R is illuminated with illumination system 12, byillumination light IL, which has passed through reticle R whose patternsurface is disposed almost coincident with a first plane (an objectplane) of projection optical system 16 b, a reduced image of a circuitpattern (a reduced image of a part of the circuit pattern) of reticle Rwithin illumination area IAR is formed via projection optical system 16b (projection unit 16) onto an area (hereinafter, also referred to as anexposure area) IA, conjugate with illumination area IAR described above,on wafer W whose surface is coated with resist (sensitive agent) andwhich is disposed on a second plane (an image plane) side of projectionoptical system 16 b. Then, by synchronous driving of reticle stage 14and wafer stage 22, reticle R is moved in the scanning direction (theY-axis direction) relative to illumination area IAR (illumination lightIL) and also wafer W is moved in the scanning direction (the Y-axisdirection) relative to exposure area IA (illumination light IL), andthereby scanning exposure of one shot area (a divided area) on wafer Wis performed and the pattern of reticle R is transferred onto the shotarea. That is, in the present embodiment, a pattern is generated onwafer W by illumination system 12, reticle R and projection opticalsystem 16 b, and the pattern is formed on wafer W by exposure of asensitive layer (a resist layer) on wafer W with illumination light IL.

Wafer stage device 20 is equipped with wafer stage 22 disposed above abase board 28. Wafer stage 22 includes a stage main body 24, and a wafertable 26 mounted on stage main body 24. Stage main body 24 is supportedon base board 28, via a clearance (an interspace, or a gap) of aroundseveral μm, by noncontact bearings (not illustrated), e.g., airbearings, fixed to the bottom surface of stage main body 24. Stage mainbody 24 is configured drivable relative to base board 28 in directionsof three degrees of freedom (X, Y, θz) within a horizontal plane, by awafer stage drive system 36 (not illustrated in FIG. 1, see FIG. 6)including, for example, a linear motor (or a planar motor). Wafer stagedrive system 36 includes a fine drive system that finely drives wafertable 26 relative to stage main body 24 in directions of six degrees offreedom (X, Y, Z, θx, θy and θz). Positional information of wafer table26 in the directions of six degrees of freedom is constantly measured ata resolution of, for example, around 0.5 to 1 nm with a wafer stageposition measurement system 38 including, for example, an interferometersystem (or an encoder system). The measurement values of wafer stageposition measurement system 38 are sent to main controller 30 (notillustrated in FIG. 1, see FIG. 6). Main controller 30 controls theposition (and the velocity) of wafer table 26 by calculating theposition of wafer table 26 in the directions of six degrees of freedomon the basis of the measurement values of wafer stage positionmeasurement system 38 and controlling wafer stage drive system 36 on thebasis of this calculation result. Main controller 30 also controls theposition of stage main body 24 within the XY plane on the basis of themeasurement values of wafer stage position measurement system 38.

Here, as a detection subject by alignment system 50, at least onegrating mark GM as illustrated in FIG. 2a is formed in each shot area onwafer W. Note that actually grating mark GM is formed in a scribe lineof each shot area.

Grating mark GM includes a first grating mark GMa and a second gratingmark GMb. The first grating mark GMa is made up of a reflection-typediffraction grating in which grating lines extending in a direction(hereinafter, referred to as an α direction for the sake of convenience)that is at a 45 degree angle with respect to the X-axis within the XYplane are formed at a predetermined interval (a predetermined pitch) ina direction (hereinafter, referred to as a β direction for the sake ofconvenience) orthogonal to the α direction within the XY plane, andwhich has a period direction in the β direction. The second grating markGMb is made up of a reflection-type diffraction grating in which gratinglines extending in the β direction are formed at a predeterminedinterval (a predetermined pitch) in the α direction, and which has aperiod direction in the a direction. The first grating mark GMa and thesecond grating mark GMb are disposed consecutively (adjacently) in theX-axis direction so that the positions of the first grating mark GMa andthe second grating mark GMb in the Y-axis direction are the same. Notethat, in. FIG. 2a , the pitch of the grating is illustrated considerablywider than the actual pitch for the sake of convenience forillustration. The same is true for diffraction gratings illustrated inthe other drawings. Incidentally, the pitch of the first grating markGMa and the pitch of the second grating mark Gmb may be the same or maybe different from each other. Further, although the first grating markGMa and the second grating mark GMb are in contact with each other inFIG. 2, they need not be in contact with each other.

Referring back to FIG. 1, multipoint fecal position measurement, system40 is a position measurement device of an oblique incidence method thatmeasures positional information of wafer W in the Z-axis direction,which has a configuration similar to the one disclosed in, for example,U.S. Pat. No. 5,448,332 and the like. Multipoint focal positionmeasurement system 40 is disposed on the further −Y side of alignmentsystem 50 disposed on the −Y side of projection unit 16. Since theoutput of multipoint focal position measurement system 40 is used forautofocus control that will be described later, multipoint focalposition measurement system 40 is referred to as an AF system 40hereinafter.

AF system 40 is equipped with: an irradiation system that irradiates thewafer W surface with a plurality of detection beams; and a beamreceiving system that receives reflection beams, from the wafer Wsurface, of the plurality of detection beams (none of these systems isillustrated). A plurality of detection points of AF system 40(irradiation points of the detection beams) are disposed at apredetermined interval along the X-axis direction on a surface to bedetected, though the illustration of the detection points is omitted. Inthe present embodiment, for example, the detection points are disposedin a matrix shape having one row and K columns (M is a total number ofthe detection points) or 2 rows and N columns (N is a half of the totalnumber of the detection points). The output of the beam receiving systemis supplied to main controller 30 (see FIG. 6). Main controller 30obtains positional information in the Z-axis direction of the wafer Wsurface (surface position information) at the plurality of detectionpoints on the basis of the output of the beam receiving system. In thepresent embodiment, a detection area of the surface position informationby AF system 40 (a disposed area of the plurality of detection points)is set in a band-shaped area extending in the X-axis direction, asillustrated by providing the same reference sign as AF system 40 inFIGS. 8a to 8c . Further, the length in the X-axis direction of thedetection area by AF system 40 is set equal to at least the length inthe X-axis direction of one shot area set on wafer W.

Prior to an exposure operation, main controller 30 moves wafer Wrelative to the detection area of AF system 40 in the Y-axis directionand/or the X-axis direction as needed, and acquires the surface positioninformation of wafer W on the basis of the output of AF system 40 atthat time. Main controller 30 performs the acquisition of the surfaceposition information as described above for all the shot areas set onwafer W, and associates the results of the acquisition with thepositional information of wafer table 26 to store them as focus mappinginformation.

As illustrated in FIG. 3, alignment system 50 is equipped with: anobjective optical system 60 including an objective lens 62; anirradiation system 70; and a beam receiving system 80.

Irradiation system 70 is equipped with: a light source 72 that emits aplurality of measurement beams L1 and L2; a movable mirror 74 disposedon optical paths of measurement beams L1 and L2; a half mirror (a beamsplitter) 76 that reflects parts of measurement beams L1 and L2reflected by movable mirror 74 toward wafer W and transmits the rest ofthe measurement beams; a beam position detection sensor 78 disposed onoptical paths of measurement beams L1 and L2 transmitted (having passed)through half mirror 76; and the like.

Light source 72 emits a pair of measurement beams L1 and L2 having abroadband wavelength, to which the resist coated on wafer W (see FIG. 1)is insensitive, in the direction. Note that, in FIG. 3, the optical pathof measurement beam L2 overlaps with the optical path of measurementbeam L1, on the depth side of the paper surface. In the present firstembodiment, as measurement beams L1 and L2, for example, white light isused.

As movable mirror 74, for example, the well-known galvano mirror is usedin the present embodiment. Movable mirror 74 has a reflection surfacefor reflecting measurement beams L1 and L2 that is configured capable ofmoving rotationally (rotating) around an axis line parallel to theX-axis. The angle of rotational movement of movable mirror 74 iscontrolled by main controller 30 (not illustrated in FIG. 3, see FIG.6). The angle control of movable mirror 74 will be further describedlater. Incidentally, an optical member (e.g., a prism or the like) otherthan the galvano mirror may be used, as far as such an optical membercan control the reflection angle of measurement beams L1 and L2.

The position (the angle of a reflection surface) of half mirror 76 isfixed, which is different from movable mirror 74. The optical paths ofthe parts of measurements beams L1 and L2 reflected off the reflectionsurface of movable mirror 74 are bent to the −Z direction by half mirror76, and then the parts of measurements beams L1 and L2 are transmitted(pass) through the center portion of objective lens 62 to be incidentalmost perpendicularly on grating mark GM formed on wafer W. Note that,in FIG. 3, movable mirror 74 is inclined at a 45 degree angle withrespect to the Z-axis, and the parts of measurement beams L1 and L2 frommovable mirror 74 are reflected off half mirror 76 in a directionparallel to the Z-axis. Further, although only movable mirror 74 andhalf mirror 76 are disposed on the optical paths of measurement beams L1and L2 between light source 72 and objective lens 62 in FIG. 3,irradiation system 70 is configured so that measurement beams L1 and L2emitted from objective lens 62 are almost perpendicularly incident ongrating mark GM formed on wafer W even in the case where movable mirror74 is inclined at an angle other than a 45 degree angle with respect tothe Z-axis. In this case, on the optical paths of measurement beams L1and L2 between light source 72 and objective lens 62, at least oneoptical member that is different from movable mirror 74 and half mirror76 may be disposed. Measurement beams L1 and L2 having passed(transmitted) through half mirror 76 are incident on beam positiondetection sensor 73 via a lens 77. Beam position detection sensor 78 hasa photoelectric conversion element such as a PD (Photo Detector) arrayor a CCD (Charge Coupled Device), and its imaging plane is disposed on aplane conjugate with the wafer W surface.

Here, as illustrated in FIG. 2 a, the distance between measurement beansL1 and L2 is set so that, of measurement beams L1 and L2 emitted fromlight source 72, measurement beam L1 is irradiated on the first gratingmark GMa and measurement beam L2 is irradiated on the second gratingmark GMb, In alignment system 50, when the angle of the reflectionsurface of movable mirror 74 is changed, the respective incidence(irradiation) positions of measurement beams L1 and L2 on grating marksGMa and GMb (wafer W) are changed in the scanning direction (the Y-axisdirection) in accordance with the angle of the reflection surface ofmovable mirror 74 (see outlined arrows in FIG. 2a ). Further, inconjunction with the positional change on grating mark GM of measurementbeams L1 and L2, the incidence positions of measurement beams L1 and L2on beam position detection sensor 78 (see FIG. 3) are also changed. Theoutput of beam position detection sensor 78 is supplied to maincontroller 30 (not illustrated in FIG. 2a , see FIG. 6). Main controller30 can obtain irradiation position information of measurement beams L1and L2 on wafer W on the basis of the output of beam position detectionsensor 78.

Here, as illustrated in FIG. 1, since alignment system 50 is disposed onthe +Y side further than AF system 40 described above, the detectionarea (the detection point) of alignment system 50 is disposed or the +Yside with respect to the detection area of AF system 40, as illustratedby providing the same reference sign as alignment system 50 in FIGS. 8ato 8 c. However, the disposed positions are not limited thereto, andthese detection areas may overlap with each other in the Y-axisdirection.

Objective optical system 60 is equipped with objective lens 62, adetector-side lens 64, and a grating plate 66. In alignment system 50,when measurement bean L1 is irradiated or the first grating mark GMa(see FIG. 2a ) in a state where grating mark GM is located directlyunder objective optical system 60, a plurality (according to beams witha plurality of wavelengths included in white light) of ±first-orderdiffraction beams ±L3, based on measurement beam L1, generated from thefirst grating mark GMa are incident on objective lens 62. Similarly,when measurement beam L2 is irradiated on the second grating mark GMb(see FIG. 2a ), a plurality of ±first-order diffraction beams ±L4, basedon measurement, beam L2, generated from the second grating mark GMb areincident on objective lens 62. The respective optical paths of the±first-order diffraction beams ±L3 and ±L4 are bent by objective lens62, and the ±first-order diffraction beams ±L3 and ±L4 are each incidenton detector-side lens 64 disposed above objective lens 62. Detector-sidelens 64 condense each of the ±first-order diffraction beams ±L3 and ±L4on grating plate 66 disposed above the foregoing detector-side lens 64.

On grating plate 66, as illustrated in FIG. 4, readout diffractiongratings Ga and Gb extending in the Y-axis direction are formed. Readoutdiffraction grating Ga is a transmission type diffraction grating thatcorresponds to grating mark GMa (see FIG. 2a ) and has a perioddirection in the β direction. Readout diffraction grating Gb is atransmission type diffraction grating that corresponds to grating markGMb (see FIG. 2a ) and has a period direction in the a direction. Notethat, in the present embodiment, the pitch of readout diffractiongrating Ga is set to be substantially the same as the pitch of gratingmark GMa. Further, the pitch of readout diffraction grating Gb is set tobe substantially the same as the pitch of grating mark GMb.

Beam receiving system 80 is equipped with: a detector 84; an opticalsystem 86 that guides, to detector 84, light corresponding to images(interference fringes) formed on grating plate 66 (readout diffractiongratings Ga and Gb) by interference between the diffraction beams (±L3and ±L4) based on measurement beams L1 and L2, as will be describedlater; and the like.

The light corresponding to the images (the interference fringes) formedon readout diffraction gratings Ga and Gb is guided to detector 84 via amirror 86 a that optical system 86 has. In alignment system 50 of thepresent embodiment, optical system 86 has a spectral prism 86 b, whichcorresponds to white light being used as measurement beams L1 and L2.The light from grating plate 66 is spectrally split, for example, intorespective colors of light, i.e., blue light, green light and red light,via spectral prism 86 b. Detector 84 has photodetectors PD1 to PD3 thatare independently provided corresponding to the respective colorsdescribed above. The output of each of photodetectors PD1 to PD3 thatdetector 84 has is supplied to main controller 30 (not illustrated inFIG. 3, see FIG. 6).

From the output of each of photodetectors PD1 to PD3, a signal (aninterference signal) having a waveform as illustrated in FIG. 5a isobtained, as an example. Main controller 30 (see FIG. 6) obtains theposition of each of grating marks GMa and GMb, by calculation, from thephase of the signal described above. That is, in exposure apparatus 10(see FIG. 1) of the present embodiment, alignment system 50 and maincontroller 30 (see FIG. 6 for each of them) configure an alignment,device for obtaining positional information of grating mark GM formed onwafer W.

When performing position measurement of grating mark GM using alignmentsystem 50, main controller 30 (see FIG. 6) controls movable mirror 74while driving grating mark GM (i.e., wafer W) relative to alignmentsystem 50 as shown by a double-headed arrow in FIG. 3, and therebycauses measurement beams L1 and L2 to follow grating mark GM and scansmeasurement beams L1 and L2 in the Y-axis direction (see FIG. 2a ).Accordingly, since grating mark GM and grating plate 66 are relativelymoved in the Y-axis direction, interference fringes are imaged (formed)on readout diffraction gratings Ga and Gb which grating plate 66 has,respectively, by interference between the diffraction beams based onmeasurement beam L1 and interference between the diffraction. beamsbased on measurement beam L2. The interference fringes imaged on gratingplate 66 are detected by detector 84 as previously described. The outputof detector 84 is supplied to main controller 30. Incidentally, thewaveform as illustrated in FIG. 5a is generated on the basis or relativemovement between grating marks GMa and GMb, and readout diffractiongratings Ga and Gb (see FIG. 4), and therefore as generated irrespectiveof the positions of measurement beams L1 and L2 irradiated on gratingmarks GMa and GMb. Consequently, the movement of grating marks GMa andGMb (i.e., wafer stage 22) and the scanning of measurement beams L1 andL2 do not necessarily have to be completely in synchronization (theirvelocities do not strictly have to be coincident).

Here, in the present embodiment, while grating mark GM is moved in theY-axis direction, the irradiation points of the measurement, beams aremoved in the Y-axis direction so as to follow the grating mark GM, andtherefore the absolute value of the position of grating nark GM on waferW is obtained in the method described below. Incidentally, in the casewhere the positions within the XY plane of the irradiation points of themeasurement beams irradiated from alignment system 50 are fixed as inthe conventional case, the absolute value of the position of gratingmark GM can be obtained on the basis of the center of the output (thewaveform similar to the one as illustrated in FIG. 5a ) of the alignmentsystem.

Separately from the waveform as illustrated in FIG. 5a (hereinafter,referred to as a first waveform), main controller 30 generates awaveform as illustrated in FIG. 5b (hereinafter, referred to as a secondwaveform). The signals indicated by the first waveform and the secondwaveform are those generated by convolution of the measurement beams,readout diffraction gratings Ga and Gb, and grating mark GM. Here, thehorizontal axis of the first waveform shows the Y coordinate value ofwafer table 26, while the horizontal axis of the second waveform showsthe difference between the Y position of the measurement beams and the Ycoordinate value of wafer table 26 that is obtained on the basis of theoutput of beam position detection sensor 78 of alignment system 50 andthe output of wafer stage position measurement system 38. That is, thefirst waveform and the second waveform are both output ted when themeasurement beams traverse one grating mark GM in the scanningdirection, though the horizontal axes are set differently from eachother. Of these waveforms, the first waveform is a waveform that shows aperiodic signal obtained by the interference fringes imaged on readoutdiffraction gratings Ga and Gb by the interference between apredetermined-order diffraction beams, e.g., the ±first-orderdiffraction beams generated at grating mark GM, and shows that theentire measurement beams are located in grating mark GM (i.e., a part ofthe measurement beams does not positioned on an edge portion of gratingmark GM), during a predetermined period of time in which the intensityis constant (the range shaded in FIG. 5a ).

On the other hand, the second waveform is a waveform that shows theposition related to grating mark GM to some extent and the shape thereofby subtracting the position of the wafer stage from the bean positionsof the measurement beams. Specifically, an envelope of the secondwaveform shows the overlapping of the measurement beams and grating markGM on the wafer, and the starting point to the end point of thisenvelope is to show the outline position and shape of grating mark GM.Note that a midpoint between the starting point and the end point of theenvelope of the second waveform is to show the center of grating markGM.

Main controller 30 obtains the approximate position (the rough position)of the grating mark from the center position of the second waveform bycalculation. the approximate position can be obtained with thewell-known method such as a slice method, for example, using the edgeportion of the second waveform in which the signal intensity increases,as the calculation.

Next, main controller 30 obtains the mark position from the firstwaveform (phase) with, for example, the well-known method such as fastFourier transformation. At this time, main controller 30 uses only datain which the measurement beams are completely within grating mark GM(data within the range shaded in FIG. 5a ).

FIG. 5c is a concept view of the calculation method of the absolutevalue of grating mark GM. In FIG. 5c , a plurality of lines that areshort in a vertical axis direction (short lines) mean the position ofgrating mark GM that is supposed from the first waveform, and each ofthese plurality of short lines corresponds to the peak of the firstwaveform in FIG. 5a . Note that, although six short lines that are closeto a long line, which will be described later, are representativelyillustrated in FIG. 5c , actually the short lines more than six appear.Further, in FIG. 5c , one long line elongated in the vertical axisdirection (a long line) means the rough position of grating mark GM(e.g., the position in the center of grating mark GM described above)obtained from the second waveform, and the short line (a candidate forthe mark position) that is closest to this long line (the rough positionof the grating mark) indicates the absolute value of grating mark GM onwafer W (the absolute position related to the center of grating markGM).

Incidentally, since alignment system 50 scans the measurement beams inthe Y-axis direct ion in the present embodiment, the absolute value ofgrating mark GM related to the Y-axis direction can be obtained with themethod described above. However, in order to obtain the absolute valuerelated to the X-axis direction, for example, it is preferable thatwafer W (grating mark GM) and alignment system 50 are relatively movedin the X-axis direction (this is similarly applied to the secondembodiment to be discussed later).

Specifically, by causing the measurement beams and grating mar GM torelatively meander (to move in directions intersecting the X-axis andthe Y-axis (e.g., directions that is at a +45 degree angle and a −45degree angle with respect to the X-axis and the Y-axis)), and scanningthe measurement beams in the X-axis direction, the edge portion ofgrating mark GM is detected. Alternatively, it is preferable that themeasurement beams and grating mark GM are relatively moved in the X-axisdirection only once so that the edge portion of grating mark GM can bedetected in the X-axis direction similarly to the Y-axis direction.Incidentally, an operation of detecting the edge portion of grating markGM by causing the measurement beams and grating mark GM to relativelymeander and scanning the measurement beams in the X-axis direction maybe performed with respect to, for example, a grating mark GM (1^(st)grating mark), as a target, that is formed in the first shot area to bedescribed later and is measured first by alignment system 50.Alternatively, an operation of scanning the measurement beams in theX-axis direction only once and detecting the edge portion of gratingmark GM may be performed with respect to, for example, a grating mark GM(1^(st) grating mark), as a target, that is formed in the first shotarea to be described later and is measured first by alignment system 50.Incidentally, the period directions of a pair of grating mark GMa andGMb may be slightly shifted without making the period directionsorthogonal.

Next, an exposure operation using exposure apparatus 10 of FIG. 1 willbe discussed using a flowchart illustrated in FIG. 7. The exposureoperation described below is performed under the control of maincontroller 30 (see FIG. 6).

Main controller 30 loads wafer W subject to exposure onto wafer stage 22(see FIG. 1 for each of them) in Step S10. At this time, wafer stage 22is positioned at a predetermined loading position on base board 28 (seeFIG. 1).

When the wafer loading is completed, main controller 30 performs afirst-time calibration (calibrating) of AF system 40 and alignmentsystem 50 in the next step, Step S12. In the present embodiment, asillustrated in FIG. 8a , the first-time calibration is performed using afirst measurement mark (a fiducial mark) WFM1 that wafer stage 22 has.In wafer stage 22 of the present embodiment, wafer W is held by a waferholder (not illustrated) disposed in the center of the upper surface ofwafer table 26 (see FIG. 1), and the first measurement mark WFM1 isdisposed at a position on the +Y side and the −X side in an outside areaof the wafer holder on the upper surface of wafer table 26. Further, ata position on the −Y side and the +X side in the outside area of thewafer holder on the upper surface of wafer table 26, a secondmeasurement mark WFM2 is disposed that is used when a second-timecalibration, which will be described later, is performed.

On each of the first measurement mark WFM1 and the second measurementmark WFM2, a reference surface for performing calibration of AF system40 and a reference mark for performing calibration of alignment system50 are formed (none of the reference surface and the reference mark isillustrated). The configurations of the first measurement mark WFM1 andthe second measurement mark WFM2 are substantially the same except fortheir different disposed positions

For a first-time calibration operation, main controller 30 drives waferstage 22 to position the first measurement mark WFM1 so as to be locateddirectly under AF system 40 and alignment system 50. Incidentally, theloading position described above may be set so that the firstmeasurement mark WFM1 is located directly under AF system 40 andalignment system 50 in a state in which wafer stage 22 is located at theloading position described above.

In the calibration operation in the present step, Step S12, maincontroller 30 performs the calibration of AF system 40 using thereference surface on the first measurement mark WFM1, and also causesalignment system 50 to measure the reference mark on the firstmeasurement mark WFM1. Then, main controller 30 obtains positionalinformation of (the detection center of) alignment system 50 within theXY plane on the basis of the output of alignment system 50 and theoutput of wafer stage position measurement system 38. The reference markfor performing the calibration of alignment system 50 is substantiallythe same as grating mark GM (see FIG. 2a ) formed on wafer W.

When the first-time calibration completed, main controller 30 startsalignment measurement and surface position measurement in the next step,Step S14. Therefore, main controller 30 positions a first shot area soas to be located directly under AF system 40 and alignment system 50, bydriving wafer stag 22. Here, the first shot area refers to a shot areato which the alignment measurement and the surface position measurementare performed first among all shot areas subject to detection, and inthe present embodiment, refers to, for example, a shot area on theutmost +Y side among a plurality of shot areas arrayed on the utmost −Xside.

Here, in the present embodiment, since the detection area of AF system40 is disposed on the −Y side relative to the detection area ofalignment system 50, the surface position information of a shot area isobtained before grating mark GM formed in the shot area. Then, maincontroller 30 controls the position and the attitude in the Z-axisdirection (the tilt in the θx direction and the θz direction) of wafertable 26 on the basis of the surface position information describedabove and the offset value that has been obtained beforehand for eachlayer, and thereby causes objective optical system 60 of alignmentsystem 50 to focus on grating mark GM subject to detection. In thepresent embodiment, the offset value described above refers to themeasurement value of AF system 40 that is obtained when the position andthe attitude of wafer table 26 are adjusted so that the signal intensity(the contrast of the interference fringes) of alignment system 50 ismaximized. In this manner, in the present embodiment, the position andthe attitude of wafer table 26 are controlled in almost real time, byusing the surface position information of wafer W obtained immediatelybefore the detection of grating mark GM by alignment system 50. Notethat there is no inconvenience even if the light from grating mark GMsubject to position measurement is not received and the surface positionof wafer W is not detected, concurrently with the position measurementof grating mark GM.

Next, an alignment operation performed in Step S14 will be described onthe basis of a flowchart in FIG. 9.

In step S30, main controller 30 measures grating mark GM (see FIG. 2a )formed in the first shot area using alignment system 50 (see FIG. 1).Note that grating mark GM formed in the first shot area is also referredto as a “first mark”. Here, in the case where wafer W is not correctlyplaced at a predetermined position in design on wafer stage 22 at thetime of the wafer loading in Step S10 described above (including thecase where a rotational shift exists), alignment system 50 cannot detectgrating mark GM.

Thus, in the case where grating mark GM in the first shot area could notbe detected (the “NO” judgment in Step S32), main controller 30 makesthe procedure proceed to Step S34 and performs a search alignmentoperation of wafer W. The search alignment operation is performed using,for example, a cutout formed on the outer circumferential edge of waferW, or a search mark formed on wafer W (none of the cutout and the searchmark is illustrated), and main controller 30 controls the position(including the rotation in the θz direction) of wafer stage 22 on thebasis of the result of the search alignment operation, and makes theprocedure return to Step S30. In the case where grating mark GM in thefirst shot area could be detected, the procedure proceeds to Step S36.

Incidentally, in the case where grating mark GM in the first shot areaon wafer W could not be detected in Step S32 described above, (the “NO”judgment in Step S32), such wafer W may be rejected. In this case, maincontroller 30 drives wafer stage 22 to a predetermined unloadingposition (which may share the same position as the loading position),and detaches wafer W from wafer stage 22 as well as making the procedurereturn to Step S10 and placing another wafer on the wafer stage 22.

Incidentally, the position of grating mark GM or the search markdescribed above in predetermined shot areas (e.g., arbitrary numbers ofshot areas) on wafer W may be roughly (with a coarse precision comparedwith the alignment measurement in Step S11) measured beforehand(referred to as “prior measurement step”), for example, using alignmentsystem 50. This prior processing allows the positional information ofwafer W loaded on wafer stage 22 to be grasped with better precision,and thus the situation can be suppressed in which grating mark GM in thefirst shot area on wafer W is not detected in Step S32 described above.Incidentally, grating mark GM or the search mark in this priormeasurement step may also be included in the “first mark” describedabove.

In Step S36, main controller 30 obtains the absolute value of theposition of grating mark GM using the foregoing method (see FIGS. 5a to5c ), on the basis of the output of alignment system 50. Main controller30 obtains a shift amount between the center in the X-axis direction ofthe measurement beams irradiated from alignment system 50 and the centerin the X-axis direction of grating mark GM, on the basis of thepositional information of that grating mark GM and the positional in ofalignment system 50 obtained in the calibration operation describedabove (see Step S12).

Here, although the “shift amount” between the center in the X-axisdirection of the measurement beams and the center in the X-axisdirection of grating mark GM is preferably obtained as a “shift amount”at the edge portion of grating mark GM in the −Y direction, it may beobtained at an arbitrary position of grating mark GM in the Y-axisdirection. For example, the “shift amount” may be obtained as a “shiftamount” near the center in the Y-axis direction of grating mark GM.Further, in the “shift amount” between the center in the X-axisdirection of the measurement beams and the center in the X-axisdirection of grating mark GM, the trajectory from the edge portion ofgrating mark GM in the +Y direction (i.e., the starting point where themeasurement beam reaches grating mark GM) may be taken into account.

Subsequently, main controller 30 judges in Step S38 whether or not theresult (the shift amount) obtained in Step S36 is greater than apredetermined permissible value. In this judgement, if the shift amountis equal to or greater than the permissible value (the “NO” judgment inStep S38), then the procedure proceeds to Step S40. On the contrary, ifthe shift amount is less than the permissible value (the “YES” judgmentin Step S38), then the procedure proceeds to Step S42.

In Step S42, as illustrated in FIG. 10, main controller 30 relativelymoves wafer stage 22 and the irradiation points on wafer W of themeasurement beams irradiated from alignment system 50 in accordance withthe shift amount obtained in Step S36 described above, therebyperforming position measurement of grating mark GM that serves as thesecond detection subject while correcting the position of theirradiation points on grating mark GM of the measurement beams. Notethat at least one of a plurality of grating marks GM, which server asthe second and subsequent detection subjects, corresponds to a “secondmark” in the present embodiment. Incidentally, although grating mark GMillustrated in FIG. 2a as described above is actually used as gratingmarks GM in FIG. 10, grating marks GM as illustrated in FIG. 10 that areorthogonal to the X-axis and the Y-axis may be used.

Since this control for correcting the X-position of wafer stage 22 isperformed in order to make the measurement beams emitted from alignmentsystem 50 coincide with the center of grating marks GM that serve as thesecond and subsequent detection subjects, the control is hereinafterreferred to as tracking control. Here, grating mark GM serving as thesecond detection subject may be formed in the first shot area, or may beformed in another shot area. Further, main controller 30 may estimatethe center positions of grating marks GM serving as the second andsubsequent detection subjects in accordance with the shift amountobtained in Step S36 described above.

Note that, although it is depicted in FIG. 10 that the measurement beamis scanned with respect to wafer W in a meandering manner by being movedin the −X direction and the −Y direction and then in the +X directionand the −Y direction relative to wafer W, actually in the presentembodiment, wafer stage 22 moves in the +Y direction while finely movingrelative to the measurement beams (alignment system 50) in the +Xdirection or the −X direction. Incidentally, wafer stage 22 should movein the X-axis direction relative to the measurement beams (alignmentsystem 50), and therefore, alignment system 50 may be configured movablein the X-axis direction, and the measurement beam may be finely drivenin the +X direction or the −X direction relative to wafer W that ismoved in the Y-axis direction, or both wafer W and the measurement beams(alignment system 50) may be finely driven in the +X direction or the −Xdirection as needed.

When the position measurement of grating marks GM formed in a pluralityof shot areas included in the first row (the row on The utmost −X side)is completed by driving wafer stage 22 in the +Y direction, maincontroller 30, as shown by arrows in FIG. 8b , moves wafer stage 22relative to alignment system 50 by a width of one shot area in the −Xdirection and also moves wafer stage 22 in the −Y direction (reverse themovement direction in the Y-axis direction), and thereby performs theposition measurement of grating mark GM (see FIG. 2a ) formed in each ofa plurality of shot areas included in the second row. After that, theposition measurement of all of grating marks GM subject to detection isperformed, by appropriately switching the movement of wafer stage 22 inthe −X direction and the movement in the +Y direction or the −Ydirection. Incidentally, the number of movements in the X-axis directionand the Y-axis direction can be changed as needed, depending on thenumber and the placement of the shot areas set on the wafer.

Here, since the influence of vibration of the apparatus can be reducedby averaging the detection results (a so-called moving average), thelonger period of time for detection of the grating marks is preferable.On the other hand, in the present embodiment, the detection of gratingmarks GM is performed while moving wafer W relative to alignment system50 (to be more detailed, readout diffraction gratings Ga and Gb (seeFIG. 4) that alignment system 50 has), which makes it difficult tosecure the long period time for detection. Therefore, when performingthe position measurement of a plurality of grating marks included in onerow by driving wafer stage 22 in the Y-axis direction, main controller30 controls the velocity of wafer stage 22 in the manner as describedbelow.

Main controller 30 decreases the measurement velocity (the movementvelocity of wafer stage 22 and the scanning velocity of the measurementbeams) of grating mark GM in the first shot area (grating mark GM forobtaining the positional shift amount described above), compared withthe measurement velocity of grating marks GM in the subsequent shotareas. For example, after the measurement of grating mark GM in thefirst shot area (corresponding to the first mark), main controller 30performs the control of increasing the movement velocity of wafer stage22. More specifically, after measuring grating nark GM in the first shotarea while moving wafer stage 22 at the first velocity, main controller30 gradually increases the measurement velocity of grating marks GM(corresponding to the second marks) subject to detection arrayed inorder from the +Y side. Incidentally, after measuring grating mark GM(the first mark) in the first shot area while moving wafer stage 22 atthe first velocity, the movement velocity of wafer stage 22 may beincreased to the second velocity, and then the subsequent grating marksGM (the second marks) may be measured. With this operation, a longperiod of time for the detection of grating mark GM to obtain the shiftamount described above can be secured, and thus the shift amountdescribed above can be more accurately obtained, and at the same timethe measurement period of time can be shortened because the distance inwhich wafer stage 22 moves can be shortened. Incidentally, not limitedto the manner described above, the measurement velocity at the time whenthe position measurement of grating marks GM subject to detectionincluded in the shot areas in the first row may be decreased, comparedwith the measurement velocity at the time when the position measurementof grating marks GM in the second and subsequent rows.

Further, at the time of position measurement of a plurality of gratingmarks arrayed in each row, the measurement velocity of the last gratingmark GM to be measured last (or several grating marks GM including thelast grating mark GM) may be decreased, compared with the measurementvelocity of grating marks GM measured before the last grating mark orthe several grating marks. In the present embodiment, as is describedabove, since the movement in the +Y direction of wafer stage 22 and themovement in the −Y direction of wafer stage 22 are switched at the timeof position measurement of grating marks GM, it is necessary todecelerate wafer stage 22 in the Y-axis direction without fail at thetime of the switching. Along with this deceleration, by decreasing themeasurement velocity of the last grating mark GM to be measured. last ineach row, the measurement accuracy of the last grating marks GM can beimproved, and at the same time the distance in which wafer sage 22 movescan be shortened, and thus the measurement period of time can beshortened.

When the position measurement of grating mark GM formed in the last shotarea (in the case where the number of rows is the odd number, the shotarea on the utmost −Y side, and in the case where the number of rows isthe even number, the shot area on the utmost +Y side) included in thelast row (the row on the utmost +X side in the present embodiment) iscompleted (the “YES” judgement in Step S44), main controller 30 makesthe procedure proceed to Step S16 in FIG. 7 and performs the second-timecalibration. In the second-time calibration, main controller 30 driveswafer stage 22 as needed, and positions the second measurement mark WFM2directly under AF system 40 and alignment system 50, as illustrated inFIG. 8c . After that, main controller 30 performs the second-timecalibration of multipoint focal position measurement system 40 andalignment system 50, using the second measurement mark WFM2.

Incidentally, in the description above, the shift amount is obtainedusing grating mark GM (i.e., one grating mark GM) in the first shot areain Step S36 (see FIG. 9), and on the basis of its result, the X-positionof wafer stage 22 is corrected as needed (Step S42, and see FIG. 10).However, the correction of the X-position is not limited thereto, andthe positions of grating marks GM in a plurality of shot areas includingthe first shot area (or a plurality of grating marks GM in the firstshot area) may be measured, and on the basis of their results, theX-position of wafer stage 22 may be corrected. In this case, forexample, it is preferable that a plurality of the grating marks aremeasured, and on the basis of their results, the movement trajectory ofwafer stage 22 is obtained as the mathematical function (e.g., thelinear function), by calculation.

Further, the position of the first shot area can be changed as needed,and it does not necessarily have to be the shot area on the utmost −Xside and the +Y side (the shot area in the vicinity of the firstmeasurement mark WFM1), and for example, the grating mark in the shotarea on the inner side of wafer W may be used. Further, the movementtrajectory of wafer stage 22 may be obtained as the mathematicalfunction (e.g., the linear function), for example, by calculation usinga plurality of grating marks around grating nark GM in the first shotarea (e.g., a plurality of grating marks included within a predeterminedradius r).

Here, when performing the foregoing position measurement of gratingmarks GM on wafer W, main controller 30 causes movable mirror 74 ofalignment system 50 to reciprocate a plurality of times (in accordancewith the number of the marks subject to detection included in one row)in conjunction with the driving of wafer stage 22 in the +Y direction orthe −Y direction. At this time, main controller 30 performs the controlso that the driving waveform of movable mirror 74 has a saw-tooth shape,as illustrated in FIG. 11. Specifically, in FIG. 11, between the pointst₁ and t₂ and between the points t₅and t₆, movable mirror 74 is drivento scan the measurement beams, and between the points t₃ and t₄ andbetween the points t₇ and t₈, movable mirror 74 is driven to be returnedto the initial position. In this manner, the velocity of movable mirror74 at the time of returning movable mirror 74 is increased, comparedwith the velocity of movable mirror 74 at the time when causing themeasurement, beams to follow in the Y-axis direction in synchronizationwith grating marks GM. Accordingly, the case where the distance betweengrating marks GM subject to detection is small can also be coped with.

When the second-time calibration is completed, main controller 30 makesthe procedure proceed to Step S18, and obtains distribution informationof the surface position of each shot area on the basis of the output ofAF system 40 acquired in Step S14, and also obtains the array coordinateof each shot area on the basis of the measurement results of alignmentsystem 50 by calculation, for example, by the method such as EnhancedGlobal Alignment (EGA) and the like. Main controller 30 performs anexposure operation of a step-and-scan method with respect to each shotarea, while driving wafer stage 22 according to the surface positioninformation described above and the results of the EGA calculation.Since this exposure operation of a step-anti-scan method is similar tothose conventionally performed, the detailed description thereof will beomitted.

According to exposure apparatus 10 related to the present firstembodiment discussed so far, the position of wafer stage 22 is correctedin accordance with the shift in the irradiation positions of themeasurement beams of alignment system 50 with respect to the firstgrating mark GM, when the measurement of the subsequent grating marks GMis performed, and therefore the positional information of grating marksGM subject to detection can be reliably obtained.

Further, alignment system 50 related to the present embodiment scansmeasurement beams L1 and L2 with respect to grating mark GM (see FIG. 3for each of them) in the Y-axis direction while moving wafer W (waferstage 22) in the Y-axis direction, and therefore, a position measurementoperation of the grating mark GM can be performed concurrently with, forexample, a movement operation of wafer stage 22 toward an exposurestarting position, which is performed after wafer W is loaded onto waferstage 22. In this case, it is preferable to dispose alignment system 50beforehand on the movement course of wafer stage 22. With thisdisposition in advance, the alignment measurement time can be shortenedand the overall throughput can be improved.

Further, alignment system 50 related to the present embodiment scans themeasurement beam so as to follow wafer W (grating mark GM) that is movedin the scanning direction, which allows the measurement for a longperiod of time to be performed. Therefore, since the so-called movingaverage of the output can be taken, the influence of the vibration ofthe apparatus can be reduced. Further, if a mark in a line-anti-spaceshape is detected using an image sensor (such as a CCD) as a beamreceiving system of the alignment system, the other images than theimages of lines completely parallel to the scanning direction cannot bedetected (such images are distorted), when the measurement beam isscanned to follow wafer W that is moved in the scanning direction. Incontrast, in the present, embodiment, since the position measurement ofgrating mark GM is performed by causing the diffraction beams from thegrating mark GM to interfere with each other, the mark detection can bereliably performed.

Further, alignment system 50 related to the present embodiment has, forexample, three photodetectors PD1 to PD3 (for blue light, green lightand red light, respectively) as detector 84, corresponding tomeasurement beams L1 and L2 that are white light. Therefore, forexample, by detecting overlay marks (not illustrated) formed on wafer Wusing the white light, and obtaining the color of light with which thecontrast of the interference fringes is the highest beforehand prior towafer alignment, and which output of the three photodetectors PD1 to PD3exemplified above is optimal to be used in the wafer alignment, can bedetermined.

Second Embodiment

Next, an exposure apparatus related to a second embodiment will bediscussed. Since the exposure apparatus related to the present secondembodiment is different only in the position of measurement mark(s) onthe wafer stage, from exposure apparatus 10 related to the firstembodiment described previously, only the difference will be describedbelow, and with regard to components that have the same configurationsand functions as those in the first embodiment, the same reference signsas those in the first embodiment will be used and the descriptionthereof will be omitted.

In the first embodiment described previously, as illustrated in thedrawings such as FIG. 8a , for example, two measurement marks WFM1 andWFM2 are disposed on wafer stage 22, while on a wafer stage 122 relatedto the present second embodiment, as illustrated in FIGS. 12a to 12d ,one measurement mark is disposed on the +Y side of a wafer holder (notillustrated) (which overlaps with wafer W in FIGS. 12a to 12d ), Anexposure operation in the present second embodiment will be describedbelow using a flowchart illustrated in FIG. 13.

Main controller 30 loads wafer W onto wafer stage 122 in Step S50 (seeFIG. 12a ). In the first embodiment described above, a calibrationoperation is performed immediately after the loading of wafer W, whilein the present second embodiment, the procedure proceeds to Step S52after the loading of wafer W, and then wafer stage 22 is driven in theXY-plane as needed and the position measurement of all grating marks GMsubject to detection is performed.

Also in a position measurement operation of grating mark GM in thepresent second embodiment, tracking processing similar to that in thefirst embodiment is performed. That is, as illustrated in a flowchart inFIG. 14 that shows a specific example of Step S52 in FIG. 13, theposition measurement of grating mark GM in the first shot (correspondingto the first mark) is performed in Step S70, and as a result of theposition measurement, in the case where the detection of grating mark GMcould not be performed (the “NO” judgement in Step S72), the procedureproceeds to Step S74 and a search alignment operation is performed, andthen the procedure returns to Step S70, in which the positionmeasurement of grating mark GM in the first shot is performed overagain. On the other hand, in the case where the position measurement ofgrating mark GM could be performed (the “YES” judgement in Step S72),the procedure proceeds to Step S76 and a positional shift amount of themeasurement beams on grating mark GM is obtained. Further, in the casewhere the positional shift amount obtained in Step S76 is less than apermissible value (the “YES” judgment in Step S78), the procedureproceeds to Step S54 in FIG. 13. On the other hand, in the case wherethe positional shift amount is equal to or greater than the permissiblevalue (the “NO” judgment in Step S78), the procedure proceeds to StepS80, the position measurement of grating mark GM in the first shot isperformed over again.

Referring back to FIG. 13, in Step S54, similarly to the firstembodiment, the measurement beam and wafer W are relatively moved in theX-axis direction (a direction of cancelling oat the positional shiftdescribed above) and also wafer W is driven in the Y-axis direction, asillustrated in FIG. 10. Alignment system 50 (see FIG. 3) performs theposition measurement of grating marks GM subject to detection whileirradiating the measurement beam onto wafer W so as to follow themovement of wafer W in the Y-axis direction. Further, the surfaceposition measurement (a focus mapping operation.) of wafer W using AFsystem 40 is also performed concurrently.

In the next step, Step 56, concurrently with the position measurementoperation of grating marks GM described above, main controller 30 judgeswhether or not the detection area of alignment system 50 and ameasurement mark WFM coincide with each other in position within the XYplane on the basis of the output of wafer stage position measurementsystem 38. As a result of this judgement, when the detection area ofalignment system 50 and measurement mark WFM coincide with each other inposition within the XY plane, the procedure proceeds to Step S58, andthe position measurement operation of grating marks GM and the focusmapping operation are suspended, and then in the next step, Step S60,the calibration operation of AF system 40 and alignment system 50 isperformed.

Then, when the calibration operation is completed, the procedureproceeds to Step S62, and main controller 30 resumes the positionmeasurement operation of grating marks GM and the focus mappingoperation. Then, when the position measurement of grating mark GM in thelast shot is completed (the “YES” judgment in Step S64), an exposureoperation of a step-and-scan method is started in Step S66. Also in thepresent second embodiment discussed so far, the effect similar to thatof the first embodiment descried above can be obtained.

Incidentally, the control method of wafer stage 22 including thetracking control related to the first embodiment and the secondembodiment described above can be changed as needed. For example, in thefirst embodiment and the second embodiment described above, in the casewhere grating mark M in the first shot area cannot be detected (the “NO”judgement in Step S32 or S72), the search alignment is performed.However, the timing of the search alignment is not limited thereto, andthe search alignment may be executed without fail after the waferloading (any period between Step S10 and Step S14, or any period betweenStep S50 and Step S54). Further, in the first embodiment and the secondembodiment described above, the foregoing prior measurement step may beexecuted without fail.

Further, in the first embodiment and the second embodiment describedabove, as illustrated in FIG. 2 a, grating marks GMa and GMb areirradiated with measurement beams L1 and L2 that correspond to gratingmarks GMa and GMb, respectively However, measurement beams are notlimited thereto, and as illustrated in FIG. 2b , a single measurementbeam L1 elongated (wide) in the X-axis direction may be irradiated ongrating marks GMa and GMb.

Further, in the first embodiment and the second embodiment describedabove, as illustrated In FIG. 2 a, grating marks GMa and GMb are arrayedalong the X-axis direction. However, the arrayed direction is notlimited thereto, and as illustrated in FIG. 2 c, grating marks GMa andGMb may be arrayed along the Y-axis direction. In this case, theposition in the X-Y plane of grating mark GM can be obtained by scanninga single measurement beam L1 in the order of grating marks GMa and GMb(or the reversed order).

Further, in the first embodiment and the second embodiment describedabove, a configuration is employed in which measurement beams L1 and L2emitted from alignment system 50 are perpendicularly incident on gratingmark GM. However, the incidence method is not limited thereto, andmeasurement beams L1 and L2 may be incident on grating mark GM at apredetermined angle (i.e., obliquely) with respect to grating mark GM.For example, as illustrated in FIG. 15 a, in the case where ameasurement beam L with a wavelength λ is made to be incident on gratingmark GM with a grating pitch p at an incident angle θ₁ with respect tothe grating mark GM, a diffraction beam L′ of a diffraction angle θ₂ isgenerated from grating mark GM, Here, the formula λ/p=sin (θ₁)+sin(θ₂)is established, and therefore, by employing the oblique incidence methodas illustrated in FIG. 15a , even if an optical system having the samenumerical aperture NA is used, the position measurement of grating markGM with a finer pitch can be performed, compared with the case wheremeasurement beam L is made to be incident perpendicularly on gratingmark GM.

Here, in the first embodiment and the second embodiment. describedabove, the position measurement of grating mark GM is performed bycausing a pair of diffraction beams from grating mark. GM to interferewith each other, and therefore, measurement beam L is irradiated ongrating mark GM from four directions in total in order to perform theposition measurement of grating mark GM (see FIG. 15a ) in theorthogonal two axis directions as illustrated in FIG. 15b , even in thecase where the oblique incidence method as illustrated in FIG. 15a isused. Here, FIG. 15b is a view showing images (directions of beams) on apupil plane of objective lens 62. As is described above, since gratingmark GM in the present embodiment (see FIG. 2) has a period direction inthe a direction or the β direction that are at, for example, a 45 degreeangle with respect to the X-axis and the Y-axis, the incidence directionof measurement beam t and the emitting direction of diffraction beam L′are also in the α direction or the β direction similarly. Incidentally,the period direction of the grating mark subject to measurement may be adirection parallel to the X-axis and the Y-axis, and in this case, asillustrated in FIG. 15 c, measurement beam L is made to be incident inthe direction parallel to the X-axis and the Y-axis. In this case,diffraction beam L′ is emitted in the direction parallel to the X-axisand the Y-axis.

Further, bean receiving system 80 of alignment system 50 in the firstembodiment described above spectrally splits white light with spectralprism 86 b. However, the spectral means is not limited thereto, and likea detection system 380 as illustrated in FIG. 16, white light may bespectrally split toward photodetectors PD1 to PD5 disposed correspondingto the respective colors of light (e.g., blue light, green light, yellowlight, red light and infrared light) by using a plurality of spectralfilters 386.

Further, illumination light IL is not limited to the ArF excimer laserbeam (with a wavelength of 193 nm), but may be ultraviolet light such asa KrF excimer laser beam (with a wavelength of 246 nm), or vacuumultraviolet light such as an F₂ laser beam ((with a wavelength of 157nm). For example, as is disclosed in U.S. Pat. No. 7,023,610, a harmonicwave, which is obtained by amplifying a single-wavelength laser beam inthe infrared or visible range emitted by a DFB semi conductor laser or afiber laser as vacuum ultraviolet light, with a fiber amplifier dopedwith, for example, erbium (or both erbium and ytterbium), and byconverting the wavelength into ultraviolet light using a nonlinearoptical crystal, may also be used. Further, the wavelength ofillumination light IL is not limited to the light having a wavelengthequal to or more than 100 nm, and the light having a wavelength lessthan 100 nm may be used, and for example, the embodiments describedabove can also be applied to an EUV (Extreme Ultraviolet) exposureapparatus that uses an EUV in a soft X-ray range (e.g., a wavelengthrange from 5 to 15 nm). In addition, the embodiments described above canalso be applied to an exposure apparatus that uses charged particlebeams such as an electron beam or an ion beam.

Further, the projection optical system in the exposure apparatus of eachof the embodiments described above is not limited to a reduction systembut may be either of an equal magnifying system or a magnifying system,and projection optical system 16 b is not limited to a dioptric systembut may be either of a catoptric system or a catadioptric system, andits projected image may be either of an inverted image or an erectedimage. Further, the configurations described in detail in the firstembodiment and the second embodiment described above, respectively, maybe arbitrarily combined to be implemented.

Further, in each of the embodiments described above, alight-transmission type mask (reticle), which is a light-transmissivesubstrate on which a predetermined light shielding pattern (or a phasepattern or a light attenuation pattern) is formed, is used. Instead ofthis reticle, however, as is disclosed in, for example, U.S. Pat. No.6,776,257, an electron mask (which is also called a variable shapedmask, an active mask or an image generator, and includes, for example, aDMD (Digital Micro-mirror Device) that is a type of a non-emission typeimage display device (spatial light modulator) or the like) on which alight-transmitting pattern, a reflection pattern, or an emission patternis formed on the basis of electronic data of the pattern that is to beexposed may also be used.

Further, each of the embodiments described above can also be applied toan exposure apparatus that performs an exposure operation in a state inwhich a space between a projection optical system and an object to beexposed (e.g., a wafer) is filled with a liquid (e.g., pure water),which is a so-called liquid immersion exposure apparatus, as isdisclosed in, for example, U.S. Pat. No. 8,004,650.

Further, each of the embodiments described above can also be applied toan exposure apparatus that is equipped with two wafer stages, as isdisclosed in, for example, U.S. Patent Application Publication. No.2010/0066992.

Further, each of the embodiments described above can also be applied toan exposure apparatus (lithography system) that forms line-and-spacepatterns on wafer W by forming interference fringes on wafer W, as isdisclosed in, for example, PCT International Publication No. 01/35168.Further, each of the embodiments described above can also be applied toa reduction projection exposure apparatus of a step-and-stitch methodthat synthesizes a shot area and a shot area.

Further, each of the embodiments described above can also be applied toart exposure apparatus that synthesizes two reticle patterns on a watervia a projection optical system and almost simultaneously performsdouble exposure of one shot area on the wafer by one-time scanningexposure, as is disclosed in, for example, U.S. Pat. No. 6,611,316.

Further, an object on which a pattern is to be formed (an object, to beexposed to which an energy beam is irradiated) in each of theembodiments described above is not limited to a wafer, but may be otherobjects such as a glass plate, a ceramic substrate, a film member, or amask blank.

Further, the use of the exposure apparatus is not limited to theexposure apparatus used for manufacturing semiconductor devices, and canbe widely applied also to, for example, an exposure apparatus formanufacturing liquid crystal display devices which transfers a liquidcrystal display device pattern onto a square-shaped glass plate, and toan exposure apparatus for manufacturing organic EL, thin-film magneticheads, imaging devices (such as CCDs), micromachines, DNA chips or thelike. Further, each of the embodiments described above can also beapplied to an exposure apparatus that transfers a circuit pattern onto aglass substrate or a silicon wafer or the like, not only when producingmicrodevices such as semiconductor devices, but also when producing areticle or a mask used in an exposure apparatus such as an opticalexposure apparatus, an EUV exposure apparatus, an X-ray exposureapparatus, or an electron beam exposure apparatus.

Electronic devices such as semiconductor devices are manufacturedthrough the steps such as: a step in which the function/performancedesign of a device is performed; a step in which a reticle based on thedesign step is manufactured; a step in which a wafer is manufacturedusing a silicon material; a lithography step in which a pattern of amask (the reticle) is transferred onto the wafer with the exposureapparatus (a pattern forming apparatus) of the embodiments describedpreviously and the exposure method thereof; a development step in whichthe wafer that has been exposed is developed; an etching step in whichan exposed member of the ether section than a section where resistremains is removed by etching; a resist removal step in which the resistthat is no longer necessary when etching is completed is removed; adevice assembly step (including a dicing process, a bonding process, anda packaging process); and an inspection step. In this case, in thelithography step, the exposure method described previously isimplemented using the exposure apparatus of the embodiments describedabove and a device pattern is formed on the wafer, and therefore, thedevices with a high integration degree can be manufactured with highproductivity.

Incidentally, the disclosures of all the publications, the PCTInternational Publications, the U.S. Patent Application Publications andthe U.S. Patents related to exposure apparatuses and the like that arecited in the description so far are each incorporated herein byreference.

While the above-described embodiments of the present invention are thepresently preferred embodiments thereof, those skilled in the art oflithography systems will readily recognize that numerous additions,modifications, and substitutions may be made to the above-describedembodiments without departing from the spirit and scope thereof. It isintended that all such modifications, additions, and substitutions fallwithin the scope of the present invention, which is best defined by theclaims appended below.

What is claimed is:
 1. A movable body apparatus, comprising: a movable body which is movable within a two-dimensional plane including a first axis and a second axis intersecting the first axis, and on which an object is placed; a mark detection system that is capable of scanning a measurement beam in a direction of the first axis, with respect to a mark of the object placed on the movable body, and capable of receiving a beam from the mark; and a control system that performs detection of the mark of the object using the mark detection system, wherein the control system: scans the measurement beam in the direction of the first axis from the mark detection system with respect to the mark of the object while moving the movable body in the direction of the first axis; detects the mark and measures a positional relationship between the mark and the measurement beam, based on a result of receiving the beam from the mark by the mark detection system, and performs adjustment of a relative position between the movable body and the measurement beam based on the positional relationship that has been measured.
 2. The movable body apparatus according to claim 1, wherein the object has the mark serving as a first mark, and a second mark different from the first mark, and the control system performs the adjustment of the relative position, and detects the second mark while moving the movable body in the direction of the first axis.
 3. The movable body apparatus according to claim 2, wherein the second mark is a mark that is detected after detection of the first mark.
 4. The movable body apparatus according to claim 2, wherein the first mark includes two or more marks, and the control system obtains a positional shift amount for each of the two or more marks, and performs the adjustment of the relative position between the movable body and the measurement beam based on the positional shift amount.
 5. The movable body apparatus according to claim 3, wherein the first mark includes two or more marks, and the control system obtains a positional shift amount for each of the two or more marks, and performs the adjustment of the relative position between the movable body and the measurement beam based on the positional shift amount.
 6. The movable body apparatus according to claim 1, wherein the adjustment of the relative position includes adjustment of the relative position in a direction of the second axis.
 7. The movable body apparatus according to claim 4, wherein the adjustment of the relative position includes adjustment of the relative position in a direction of the second axis.
 8. The movable body apparatus according to claim 5, wherein the adjustment of the relative position includes adjustment of the relative position in a direction of the second axis.
 9. The movable body apparatus according to claim 1, further comprising: a position measurement system capable of measuring position information of the movable body within the two-dimensional plane, wherein the control system detects position information of the mark using the position measurement system and the mark detection system.
 10. The movable body apparatus according to claim 1, wherein the mark detection system is capable of detecting the measurement beam irradiated on the mark, and the control system obtains the positional relationship between the mark and the measurement beam based on a result of detecting the measurement beam.
 11. An exposure apparatus, comprising: the movable body apparatus according to claim 1, in which an object provided with a mark is placed on the movable body, wherein the object placed on the movable body is exposed by being irradiated with an energy beam. 